The invention concerns a method and device for control and/or operation of equipment which is installed in marine seismic tows at a distance from a towing vessel, e.g. adjusting mechanisms for deflectors in the tow-line, tailbuoy streamers or electronic equipment, where the equipment is supplied with an energy source.
Seismic surveys at sea are conducted by towing through the water behind a vessel seismic devices which transmit seismic signal pulses to the seabed, and equipment to record the reflected signals. These seismic devices are normally placed in or along tow-lines which are pulled parallel to and at a distance from each other behind the towing vessel. The actual signal transmission for the seismic surveys is controlled in the usual way from the towing vessel by means of electrical or hydraulic trigger signals in the normal manner.
In seismic tows, however, there are a number of other elements which are more difficult to handle. Examples of such equipment are the deflectors or otter board devices which are used to pull tow-lines out to the side of the vessel and to position them in relation to the center line, where it is desirable to have adjusting mechanisms which, when activated, can effect an alteration in position in order to change the distance to other parallel tow-lines. The tow lines are also usually equipped with tailbuoys which contain equipment for recording their positions. Similar equipment can also be placed along the length of both the seismic gun cables as well as the receiver cables, the so-called streamers. The problems involved in the operation of such additional equipment in the cable have been due to the fact that this equipment has often required a relatively large power output for its operation, while it has not been possible to supply the required energy through the cables in the tow- lines, since greater amounts of energy could affect the other seismic equipment.